Fibrous insulation products are often used in heating, ventilating and air conditioning units, and in appliances such as dishwashers, refrigerators and freezers. The insulation product is usually installed inside the metal housing of the device to reduce the transmission of heat and sound. The insulation product may be attached to the inner surface of the housing by the use of tape, film or adhesive. However, tapes and films are not always effective in providing good adhesion between the insulation product and the housing.
Further, traditional methods of applying adhesive on a porous substrate such as fibrous insulation generally do not provide a strong bond between the adhesive and the substrate. The adhesive adheres only to weakly bound surface fibers and dust, and consequently the interfacial bond between the adhesive and the fibrous insulation is weak.
The prior art does not adequately address this problem. For example, U.S. Pat. No. 5,106,447 to Di Rado et al. discloses a hot melt adhesive composition for bonding an insulation assembly to a heating, ventilating or air conditioning (HVAC) unit. The adhesive is applied by spraying it onto the unit being insulated, or onto the insulation assembly. It has been found that such spray application of hot melt adhesive does not result in a strong bond between the HVAC unit and the insulation assembly because the adhesive only bonds to the top surface of the insulation assembly and the insulation assembly tends to delaminate as a result when force is applied thereto. There is no suggestion of any method other than spraying for applying the adhesive.
U.S. Pat. No. 4,134,948 to Baker, Jr. discloses a nonwoven fabric for use in industrial and household wipers. An adhesive is sprayed on one surface of the fabric, and a partial vacuum is applied on the opposed surface to saturate the fabric with adhesive. The saturated fabric is conveyed through an oven to cure the adhesive. The adhesive is thus a thermoset adhesive, as opposed to a hot melt adhesive which is thermoplastic. There is no suggestion of impinging the adhesive with a fluid, and no suggestion of leaving a portion of the adhesive on the surface of the fabric.
Accordingly, it would be desirable to provide a method for applying adhesive on a porous substrate that improves the bond strength between the adhesive and the substrate. It would particularly be desirable to provide a method for applying a pressure sensitive adhesive on a fibrous insulating material to make a convenient peel and stick insulation product.